Tidal pressures exerted by a hot Jupiter may cause its host star to spin faster than it would without the planet. Because of its faster rotation, the host star may become more active and emit more X-rays, which are typical of young stars.
A new study using NASA’s Chandra X-ray Observatory investigates whether “hot Jupiter” exoplanets can slow the aging of the stars around them. It implies that ‘hot Jupiter’ exoplanets can make their host stars appear younger than they are.
Although the anti-aging ability of the “hot Jupiter” phenomenon has been observed previously, this result is the first time it has been thoroughly documented, providing the most conclusive evidence yet for this unusual phenomenon.
“In medicine, you need a lot of patients enrolled in a study to know if the effects are real or some sort of outlier,” said Nikoleta Ilic of the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany, who led this new study. The same can be said for astronomy, and this study gives us reason to believe that these hot Jupiters are making the stars they orbit appear younger than they are.”
Several factors influence Star’s vitality. Stars’ activity and spinning rate slow as they age, and they have fewer outbursts. Astronomers have needed assistance determining whether a star is exceptionally active because it is being influenced by a nearby planet, making it appear younger than it is, or whether it is genuinely young because determining the ages of most stars is difficult.
This new study looked at double-star (or “binary”) systems in which the stars are widely separated but only one has a hot Jupiter orbiting it. Astronomers believe that stars in binary systems develop at the same time, just like human twins. The distance between the stars is far too great for them to interact or for hot Jupiter to collide with the other. This implies that they could use the planetless star as a control subject.
“It’s almost like using twins in a study where one twin lives in a completely different neighborhood that affects their health,” said co-author Katja Poppenhaeger of AIP. We can study the differences in the behaviour of the same-aged stars by comparing one star with a nearby planet to its twin without one.”
The amount of X-rays determined how “young” a star is acting. They looked for signs of planet-to-star interaction in nearly thirty X-ray systems (the final sample included 10 systems observed by Chandra and six by ESA’s XMM-Newton, with several observed by both). Because they were brighter in X-rays, they discovered that stars with hot Jupiters were more active than their partner stars without hot Jupiters.
“In previous cases, there were some very intriguing hints, but now we finally have statistical evidence that some planets are indeed influencing their stars and keeping them acting young,” said co-author Marzieh Hosseini of AIP. Hopefully, future research will uncover more systems to help us better understand this effect.”